Adjusted Cost Base in Canada: Meaning and Calculation

Adjusted cost base (ACB) is the amount used to determine a capital gain or loss when you sell an investment on capital account. You are responsible for verifying the calculation: a broker’s book value can be a useful cross-check, but CRA says T5008 Box 20 may or may not reflect ACB. This guide walks through the complete calculation, with worked examples for both stocks and ETFs.

To calculate ACB for a security in Canada:

1. Add up the total cost of every purchase, including commissions, across all your taxable accounts.
2. Adjust that total for events after purchase: add DRIP reinvestments and reinvested distributions, subtract return of capital.
3. Divide the adjusted total by the number of shares you hold to get ACB per share.
4. When you sell, subtract ACB per share × shares sold (and selling commissions) from your proceeds to get the capital gain or loss.

The sections below show each step with worked numbers. Jump to the ACB calculation example for two purchases and a partial sale, including the remaining cost base.

Want to test a simple CAD history as you read? Use the free one-security ACB calculator . It covers entered purchases, sales, DRIPs, and return of capital; the worked examples and guidance below explain the broader method and its limitations.

What adjusted cost base means

Adjusted cost base is the cost of a capital property for tax purposes after applicable adjustments. For identical securities held in taxable accounts under the same ownership, purchases and adjustments belong to one cost pool. Purchase commissions form part of that cost; selling commissions are accounted for separately when calculating the gain or loss.

Capital gain or loss = proceeds − ACB allocated to the shares sold − selling expenses.

Total ACB vs ACB per share

• Total ACB is the cost assigned to the entire remaining position after purchases, sales, and adjustments.
• ACB per share is total ACB divided by the remaining shares or units.

For example, a position with $5,000 total ACB and 100 shares has $50 ACB per share. Selling 20 shares removes $1,000 of cost, leaving 80 shares with $4,000 total ACB. The per-share ACB remains $50. Keep these two amounts separate in your records.

A broker’s displayed book value may be useful evidence, but it does not establish whether outside holdings or missing history were included. See broker book value versus adjusted cost base for the detailed comparison.

Who needs these records?

This securities guide concerns investments on capital account in non-registered taxable accounts. Keep the purchase history from the start, even if you do not plan to sell soon. Holdings inside registered plans are outside this ordinary taxable ACB pool, although registered-account transactions can matter to rules such as superficial losses .

Identical securities held by the same taxpayer at two taxable brokerages generally belong to one pool. Separate taxpayers do not share a pool merely because they use the same broker. The multi-brokerage example below shows how to allocate cost from the combined history.

The adjusted cost base formula

After each new purchase, recalculate ACB per share using:

1

New ACB per share = (Previous total ACB + New shares × Price per share + Commission) ÷ Total shares held

When you sell:

1
2

Capital gain = (Sale price per share × Shares sold) − Commission
             − (ACB per share × Shares sold)

After a partial sale, both your total ACB and share count decrease proportionately. Your ACB per share stays the same until the next purchase or an adjustment event. Keep full precision during the calculation and round only the displayed amounts.

Example 1: Simple stock purchase and sale

Purchase:

• Buy 100 shares of RY.TO at $130.00 per share
• Commission: $9.95

Total cost = (100 × $130.00) + $9.95 = $13,009.95 ACB per share = $13,009.95 ÷ 100 = $130.10

Sale (all shares):

• Sell 100 shares at $145.00 per share
• Commission: $9.95

Proceeds = (100 × $145.00) − $9.95 = $14,490.05 Capital gain = $14,490.05 − $13,009.95 = $1,480.10

To maintain these calculations over time, create a free myCostBase account and enter your supported transaction history. The application saves your records as you add purchases and sales.

ACB calculation example

Two purchases and a partial sale of a Canadian stock: buy 100 shares at $50, buy another 50 at $60, then sell 80 at $70. Each transaction has a $10 commission. All amounts are in Canadian dollars. Assume these are the only transactions in the taxable pool, with no distributions or other cost-base adjustments.

Step 1: Add both purchases to the pool

The second purchase adds (50 × $60) + $10 = $3,010 to the existing $5,010 cost pool.

Total ACB = $5,010 + $3,010 = $8,020.

ACB per share = $8,020 ÷ 150 = $53.466666…, displayed as $53.47. Use the unrounded fraction when allocating cost to a sale.

Step 2: Calculate the gain on the partial sale

On March 20, 2026, sell 80 shares at $70 with a $10 selling commission:

The selling commission is deducted once when calculating net proceeds. It is not also deducted from the cost pool.

Step 3: Carry forward the remaining ACB

After selling 80 of the 150 shares:

• Shares remaining: 150 − 80 = 70.
• Remaining total ACB: $8,020 − [80 × ($8,020 ÷ 150)] = $3,742.67, displayed to cents.
• ACB per share: still $8,020 ÷ 150 = $53.466666…, displayed as $53.47.

A partial sale reduces total ACB and share count, but does not change ACB per share. Save the transaction records and retain the unrounded calculation for later sales. Multiplying by the rounded $53.47 would incorrectly allocate $4,277.60 to this sale instead of $4,277.33.

To maintain this history as new transactions arrive, create a free myCostBase account . The application calculates ACB from your saved records; this example explains the arithmetic without requiring an account.

Adjusted cost base for stocks vs. ETFs

For individual stocks (e.g., Canadian bank stocks, Canadian railway stocks, U.S. individual equities), the ACB calculation is primarily driven by purchases, sales, commissions, and any stock splits. The mechanics are straightforward once pooling across accounts is handled correctly.

For ETFs and mutual funds, the ACB calculation is more complex because several additional annual adjustments must be applied:

• Return of capital (ROC) distributions reduce ACB each year they are paid (T3 or T5 Box shows ROC amounts)
• Reinvested capital gains distributions (phantom income) increase ACB — you pay tax on income you didn’t receive as cash, so CRA lets you add it to your cost
• DRIP reinvestments add new shares at the distribution date price, increasing both share count and total ACB

Investors in broad Canadian ETFs (XEQT, VEQT, XBAL, VBAL, etc.) often deal with small annual ROC amounts from the underlying bond allocations. U.S.-listed ETFs (VTI, QQQ, etc.) frequently have reinvested capital gains distributions that increase ACB.

For stocks, missing a stock split changes the share count and ACB per share but not the total ACB. A 2-for-1 split doubles your shares and halves the ACB per share.

Example 3: ETF with return of capital adjustment

Scenario: You hold 200 units of a Canadian bond ETF.

Purchase: 200 units at $20.00 = $4,000.00 ACB. ACB per unit = $20.00.

Year 1 distribution: ETF pays $0.30 per unit in return of capital.

ROC adjustment = 200 × $0.30 = $60.00 New total ACB = $4,000.00 − $60.00 = $3,940.00 New ACB per unit = $3,940.00 ÷ 200 = $19.70

Year 2 distribution: ETF pays $0.25 per unit in return of capital.

ROC adjustment = 200 × $0.25 = $50.00 New total ACB = $3,940.00 − $50.00 = $3,890.00 New ACB per unit = $3,890.00 ÷ 200 = $19.45

Sale after Year 2: Sell all 200 units at $21.50 per unit. Commission: $9.95.

Proceeds = (200 × $21.50) − $9.95 = $4,290.05 ACB = 200 × $19.45 = $3,890.00 Capital gain = $4,290.05 − $3,890.00 = $400.05

Without the ROC adjustments, you would have reported: $4,290.05 − $4,000.00 = $290.05 in capital gains — $110 less than the correct amount.

For more detail on how ROC works and where to find the per-unit amounts, see ETF Return of Capital and Adjusted Cost Base .

Example 4: Pooling across two brokerages

CRA treats all shares of the same security held in taxable accounts by the same investor as a single pool. If you hold 200 shares at Wealthsimple and 100 shares at Questrade, your ACB is calculated across all 300 shares.

Transaction history for XEQT:

Total pool after both purchases:

• Total shares: 300
• Total ACB: $7,854.95
• ACB per share: $7,854.95 ÷ 300 = $26.18

When you sell 50 shares from your Wealthsimple account:

• ACB deducted = 50 × ($7,854.95 ÷ 300) = $1,309.16, rounded only for display
• NOT 50 × $25.00 = $1,250.00 (the Wealthsimple-only cost)

For a full walkthrough of multi-brokerage ACB pooling, see Pooled ACB Across Multiple Brokerages .

Calculating ACB for USD stocks

Canadian capital gains are reported in Canadian dollars. For a USD-denominated security, convert the purchase cost and disposition proceeds separately using a documented exchange rate applicable to each transaction. CRA generally points to the Bank of Canada daily rate, while also accepting qualifying alternative sources and averages in certain circumstances.

Purchase:

• Buy 50 shares of AAPL at USD $175.00 on a day when 1 USD = 1.3542 CAD
• Commission: USD $1.00

CAD purchase cost = (50 × $175.00) × 1.3542 = $11,849.25 CAD CAD commission = $1.00 × 1.3542 = $1.3542 CAD Total ACB = $11,849.25 + $1.3542 = $11,850.6042 CAD, displayed as $11,850.60 CAD ACB per share = $11,850.6042 ÷ 50 = $237.01 CAD, rounded for display

Sale:

• Sell 50 shares at USD $195.00 on a day when 1 USD = 1.3210 CAD
• Commission: USD $1.00

CAD gross proceeds = (50 × $195.00) × 1.3210 = $12,879.75 CAD CAD selling commission = $1.00 × 1.3210 = $1.3210 CAD Net proceeds = $12,879.75 − $1.3210 = $12,878.4290 CAD, displayed as $12,878.43 CAD Capital gain = $12,878.4290 − $11,850.6042 = $1,027.82 CAD, rounded at the end

Note that even if the stock price rose in USD terms, the capital gain in CAD terms depends on both the price change and the exchange rate change. A weakening Canadian dollar amplifies gains; a strengthening Canadian dollar reduces them.

For exchange-traded shares, retain both trade and settlement dates; CRA’s T5008 guide uses the settlement date in Box 14. A Bank of Canada daily rate usually provides the clearest transaction-level record, but it is not the only source CRA may accept. See Bank of Canada FX rates for capital gains for rate-source criteria, date handling, and documentation.

Transactions that change your adjusted cost base

CRA adjusted cost base calculation: what the rules require

CRA’s requirement is the weighted average pooling method. Every time you buy additional shares, the new cost is averaged into the existing pool. You do not track lots separately (FIFO, LIFO, or specific-share identification are not permitted for Canadian investors in taxable accounts for identical property).

The relevant CRA guidance is in the Income Tax Act, specifically section 47 (identical properties) and section 53 (adjustments to cost base). CRA’s Capital Gains guide (T4037) also covers the mechanics in plain language.

For a capital gains claim to be defensible on audit:

• Keep records of every purchase date, price, and commission
• Document every ROC adjustment with the T3 or ETF provider data used
• Record the exchange-rate source, observation date, and rate for every USD transaction
• Maintain a running ACB ledger from first purchase through final disposition

Common ACB calculation mistakes

Mistake 1: Calculating ACB per brokerage instead of across all taxable accounts. Every brokerage sees only its own side. If you hold the same ETF at Wealthsimple and Questrade and calculate a separate ACB at each, both figures are wrong for CRA purposes. The single pooled ACB is the legal requirement.

Mistake 2: Using T5008 Box 20 without verification. Box 20 is cost or book value and may not reflect transfers, ETF adjustments, foreign exchange, superficial losses, or cross-brokerage pooling. It is a useful starting point for reconciliation, but use it only after confirming that it supports the ACB required by the applicable rules. For more on this distinction, see T5008 Box 20 and Adjusted Cost Base .

Mistake 3: Missing return of capital adjustments. ETFs that distribute ROC reduce your ACB annually. Investors who track ACB in a spreadsheet but only record buy and sell transactions miss these adjustments entirely. Over five to ten years of ROC, the cumulative error can reach thousands of dollars.

Mistake 4: Applying one annual-average FX rate without confirming it is appropriate. CRA generally points to a daily Bank of Canada rate and permits averages in certain circumstances. For discrete security purchases and dispositions, separately documented transaction-level rates usually provide a clearer audit trail and capture currency movement between the events.

Mistake 5: Not carrying ACB through transfers. When you move shares between taxable brokerages without a disposition, the supported ACB generally carries through. The receiving broker may receive correct book-cost information, an estimate, or no usable history. Verify the transferred value against the outgoing records instead of assuming either the displayed amount or current market value is correct.

Mistake 6: Forgetting DRIP shares. Every dividend reinvestment adds new shares at cost. Over years of monthly DRIP participation, the cumulative cost addition can be material. Omitting DRIP from ACB records overstates the taxable capital gain at sale.

How to track adjusted cost base

Option 1: Spreadsheet. A controlled workbook can pool identical securities across taxable brokerages and record buys, sales, DRIPs, and supported cost adjustments. The ACB spreadsheet download and instructions explain the identifiers, formulas, source references, and review flags to maintain. More accounts and adjustments increase the manual review work; they do not automatically make a spreadsheet invalid.

Option 2: Dedicated ACB software. myCostBase maintains a pooled ACB ledger across all taxable accounts, applies ETF distribution adjustments, handles Bank of Canada FX conversion automatically, and produces the reconciled capital gains detail you need for Schedule 3 at tax time. You can start with manual entry on the free plan. For account-based calculation and saved tracking across brokerages, see myCostBase .

For a side-by-side comparison of when spreadsheets are enough and when software becomes necessary, see the adjusted cost base spreadsheet guide . Before filing, work through the Canadian Adjusted Cost Base Checklist to confirm every ACB record, T5008 slip, and distribution adjustment is complete.

Records that support your ACB

Keep purchase and sale confirmations, brokerage statements, transfer history, distribution tax factors, and evidence for each adjustment. For foreign-currency transactions, retain the original amounts, exchange-rate source, relevant dates, and Canadian-dollar calculation. A final cost number without the history behind it is difficult to verify.

Your records should let you reproduce the cost pool immediately before a sale and explain the amount allocated to that disposition. Preserve full precision, link ledger rows to source documents, and keep backups of both. Use the year-round ACB recordkeeping routine for ongoing maintenance and the pre-filing checklist for final review.

Adjusted cost base in Canada: common questions

What is adjusted cost base in Canada?

Adjusted cost base is the cost of a capital property for tax purposes after applicable adjustments. For identical securities in taxable accounts under the same ownership, maintain a pooled total ACB. Divide that total by the units held to find ACB per share; allocate that per-share cost to the shares sold.

Is adjusted cost base the same as broker book value?

Not necessarily. Broker book value can be a useful cross-check, but it may omit outside holdings, transferred history, or relevant adjustments. CRA says T5008 Box 20 may or may not reflect adjusted cost base. Verify the amount against complete transaction and adjustment records.

How often do I need to recalculate ACB?

Recalculate after every event that affects cost: each purchase, each DRIP reinvestment, each ROC adjustment (annually, when T3 slips arrive), and each split or consolidation. After a partial sale, reduce total ACB by the cost allocated to the shares sold and reduce the share count. ACB per share remains unchanged.

What if I don't have the original purchase records?

CRA expects you to be able to support your capital gains calculations on audit. If records are missing, contact your broker — most maintain historical transaction records for at least seven years, though older records may be unavailable. Some investors reconstruct from brokerage statements, T5008 slips from prior years, and annual DRIP confirmation letters. Where reconstruction is necessary, document your methodology and sources.

Does ACB matter for shares held in a TFSA or RRSP?

No. Shares held in registered accounts (RRSP, TFSA, FHSA, RESP) are not subject to capital gains tax when sold. ACB tracking only applies to non-registered (taxable) accounts. If you transfer shares from a registered to a non-registered account (a rare situation), the transfer is treated as a disposition from the registered account and a new acquisition in the non-registered account at fair market value.

Can I use the FIFO method instead of weighted average?

No. Canadian tax law requires the weighted average pooling method for identical properties held in taxable accounts. You cannot designate specific lots for disposition or use FIFO/LIFO. Each time you buy, the new cost is pooled into the existing average.